Process for dehairing of skins with ultrasonic energy



United States Patent PROCESS FOR DEHAIRING OF SKINS WITH ULTRASONIC ENERGY Paul Renaut, Meaux, France, assignor to Realisations Ultrasoniques, a corporation of France No Drawing. Filed June 25, 1958, Ser. No. 744,315

Claims priority, application France June 28, 1957 4 Claims. (Cl. 8-94.16)

The present invention relates to a method of woolpulling of skins and, in a general way, to a process for unhairing such skins. It refers, more particularly, to a method using, at a certain stage during the treatment of skins, ultrasonic energy.

Wool-pulling, for instance of sheepskin, is effected, as well known, on preliminarily dried up skins. The operation consists in completely removing the woolhair, together with the bulb, if possible without injuring the skin. To this end, it is common practice to start by soaking the skins in water containing a wetting agent, wherein these skins are swelling by absorption of a certain amount of water. The operation continues thereafter by applying, according to the known art, thermal, chemical and biological treatments. For example, the thermal treatment consists in cooling the product and then applying thereto sudden heat, thus causing the skin cells to be disrupted: the woolhair is thus set free; however the resulting hide is of a substantially low-grade quality. The chemical treatment is an acid applying operation. Finally, the biological treatment consists, for instance, in an inoculation operation into the skin of certain microbe or germ strains, which cause it to decay or decompose: such an operation is however very delicate, because of the difiiculty of halting fermentation due to the inoculated germs before it will injure the skin and the wool. None of these processes and operations, as known in the art, are free from such disadvantages.

It is therefore an object of the present invention to eliminate these disadvantages and provide a method of Wool-pulling whereby the swelling of the treated skins is substantially improved with regard to conventional methods.

The method according to the invention consists essentially in submitting the skins to be treated, after a preliminary swelling operation in water, with admixture not only of a convenient wetting agent, but also of an antiseptic substance adapted to avoid fermentation in the skin and/or the hair, to a treatment by means of elastic vibrations, particularly of ultrasonic waves, during a suflicient period of time for the effect of such vibrations to provide for a subsequent easy extraction of the woolhair, and at a frequency lower than 100 kc./s.

The invention will be best understood from the following description and non limitative example of the operation of the process:

The dry skins are first steeped or soaked in water containing a convenient wetting agent and an antiseptic substance. After a period of at least about fifty hours of soaking the resulting swelling of the skin increases the 2,965,435 Patented Dec. 20, 1960 thickness thereof, for instance from 2 mm. to 4 mm.: no fermentation will occur because of the presence in the soaking bath of the antiseptic agent.

After slightly drying the skins, they are then dipped into a water tank and submitted to an ultrasonic treatment. As the equipment therefor is well known, no description of the ultrasonic generator will be given herein. A frequency comprised between about 10 and kc./s. will be used: it has been found that energy of higher frequency might injure the hide. A treatment of about 3 minutes, in the example described, was sufficient to effectively cause the ligaments holding the woolhair bulb to be separated, probably on account of the socalled cavitation phenomenon; thereafter, the removal of the wool from the skin thus prepared is readily effected, according to the common practice.

The wool and the skin do not suffer any damage or degradation thanks to this treatment. Moreover, an in crease in the swelling properties of the skin has been noted during the treatment by ultrasonic energy: the swelling increases, in the example cited, the thickness of the skin to about 6 mm., thus enabling an additional cutting to be effected. It has also been noted that the skin treated by the method according to the invention is particularly easy to be tanned.

The ultrasonic method of treatment is .readily applied to skins and hairs of fleece of various thicknesses. It may also be applied to the removal of downs, bristles, etc.

I claim:

1. A process for unhairing skins, combining the steps of submitting said skins to a swelling operation in water containing a wetting agent and an antiseptic substance and thereafter treating the skins by means of ultrasonic Waves at a frequency lower than 100 kc./s.

2. A process for wool-pulling of skins, combining the steps of submitting said skins, during at least about 50 hours, to a swelling operation in Water containing a wetting agent and an antiseptic substance, slightly drying the skins and thereafter treating the skins by means of ultrasonic waves, at a frequency between 10 kc./s. and 100 kc./s., during about 3 minutes.

3. A process for unhairing skins, combining the steps of submitting said skins to a swelling operation in water containing a wetting agent and thereafter treating the skins by means of ultrasonic waves at a frequency lower than 100 kc./s.

4. A method for unhairing skins comprising the following steps: immersing a skin into water comprising a wetting agent and an antiseptic substance; allowing said skin to swell in said water; removing said skin from said water; allowing said skin to lose a portion of the water it has retained; dipping said skin into water; and submitting said skin to ultrasonic energy of a frequency comprised between 10 kilocycles per second and 100 kilocycles per second.

References Cited in the file of this patent Manufacturing Chemist, January 1951 (XXII, I), pp. 5-8 and 12.

Rath et al.: The Influence of Ultrasonic Waves on Fibers, Am. Dyestuff Reporter, June 21, 1954, pp. 395-396 (abst. of an article appearing in Melliand Textilber, 653-6, July 1953; 763-5, August 1953). 

4. A METHOD FOR UNHAIRING SKINS COMPRISING THE FOLLOWING STEPS: IMMERSING A SKIN INTO WATER COMPRISING A WETTING AGENT AND AN ANTISEPTIC SUBSTANCE, ALLOWING SAID SKIN TO SWELL IN SAID WATER, REMOVING SAID SKIN FROM SAID WATER, ALLOWING SAID SKINS TO LOSE A PORTION OF THE WATER IT HAS RETAINED, DIPPING SAID SKIN INTO WATER, AND SUBMITTING SAID SKIN TO ULTRASONIC ENEREGY OF A FREQUENCY COMPRISED BETWEEN 10 KILOCYCLES PER SECOND AND 100 KILOCYCLES PER SECOND. 